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Posted

It takes certain fixed assumptions on important things like rolling resistance and wind resistance when doing the calcs so it'll only be truly accurate when real world conditions match their assumptions. But as a rough guide it does have some merit.

Posted

I'd be interested to see how it compares to a proper power meter, as well as that new hr based power meter.

 

HR (obviously) has nothing to do with calculating power.

 

It is relevant when comparing the same route, under the same conditions, on the same bike e.g. are you able to maintain the same power output at lower HR.

Posted (edited)

 

From a physics or mathematical perspective HR has nothing to do with power.

 

However ss there a possible correlation between HR and Power? I'm sure there is, but then there's also a correlation between HR and wind and rolling resistance. Question is do I need an algorithm to guesstimate the wind resistance and then work on my cycling posture and also predeict the rolling resistance and then I can work on my tyre tread pattern and pressures?

 

It's a prediction and basing your training on a prediction is obviously a personal choice but I always believe in doing things properly or rather not doing them.

 

From their FAQ's - I rest my case:

 

3. How accurate is it?

a. This is not as accurate as a PowerTap and not intended to replace one. Research has shown varying degrees of accuracy based on individuals and types of riding. Accuracy will depend greatly on the individual and type of riding.

4. How does it compare to PowerTap?

a. It doesn’t and isn’t intended to. The PowerTap directly measures power through strain gauges on the torque tube, which is a direct measurement of power. PowerCal is an estimated value derived from HR.

5. How, after all these years of saying HR alone is not the best measurement for training, can you now measure power from HR?

a. There has always been a correlation between HR and power, it’s just that it varies depending on conditions. We’ve simply designed algorithms which predict power based on HR.

Edited by sometime
Posted

From a physics or mathematical perspective HR has nothing to do with power.

 

However ss there a possible correlation between HR and Power? I'm sure there is, but then there's also a correlation between HR and wind and rolling resistance. Question is do I need an algorithm to guesstimate the wind resistance and then work on my cycling posture and also predeict the rolling resistance and then I can work on my tyre tread pattern and pressures?

 

It's a prediction and basing your training on a prediction is obviously a personal choice but I always believe in doing things properly or rather not doing them.

 

From their FAQ's - I rest my case:

 

3. How accurate is it?

a. This is not as accurate as a PowerTap and not intended to replace one. Research has shown varying degrees of accuracy based on individuals and types of riding. Accuracy will depend greatly on the individual and type of riding.

4. How does it compare to PowerTap?

a. It doesn’t and isn’t intended to. The PowerTap directly measures power through strain gauges on the torque tube, which is a direct measurement of power. PowerCal is an estimated value derived from HR.

5. How, after all these years of saying HR alone is not the best measurement for training, can you now measure power from HR?

a. There has always been a correlation between HR and power, it’s just that it varies depending on conditions. We’ve simply designed algorithms which predict power based on HR.

 

which is why I said I'd like to see power meter vs strava vs the new hr power meter. It would be quite useful to have a comparison of all 3

Posted

which is why I said I'd like to see power meter vs strava vs the new hr power meter. It would be quite useful to have a comparison of all 3

 

I understand that but in practical terms that's very hard to replicate:

 

Ride exactly the same route with each "power" tool, with exactly the same wind and road condtions, on exactly the same bike, doing exactly the same speed at each point on the ride, doing exactly the same HR at each point on the ride. If you can do this then the comparison is valid.

Posted

Stava's power stats are wrong unless you use a PM and have the premium upgrade. It either calculates or over calculates for some reason. I have compared Strava readings to actual PM readings.

Posted

I understand that but in practical terms that's very hard to replicate:

 

Ride exactly the same route with each "power" tool, with exactly the same wind and road condtions, on exactly the same bike, doing exactly the same speed at each point on the ride, doing exactly the same HR at each point on the ride. If you can do this then the comparison is valid.

 

Use all 3 devices for a single ride and compare their figures...

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